Which condition involves over-ventilated lungs with increased carbon dioxide retention?

• A. COPD
• B. CHF
• C. RSV
• D. TB

Answer: (A)

Chronic obstructive pulmonary disease causes airflow limitation that leads to air trapping and lung hyperinflation. Expiration becomes incomplete, so the lungs stay chronically over-inflated with an increased residual volume. In COPD, destruction of alveolar walls and mismatches in ventilation and perfusion impair effective gas exchange, allowing carbon dioxide to accumulate and be retained, especially in advanced disease. This combination—air-trapped, over-inflated lungs with increased CO2 retention—fits COPD best. Cardiogenic heart failure tends to produce edema and a different gas-exchange pattern, RSV is a viral illness primarily in children, and TB is mainly a restrictive, fibrotic process without the characteristic hyperinflation and CO2 retention of COPD.